The Operating Principle of Thermocouples

When two dissimilar metal wires are joined together at one end, a voltage is produced at the other end that is approximately proportional to temperature. That is to say, the junction of two different metals behaves like a temperature-sensitive battery. This form of electrical temperature sensor is called a thermocouple:

This phenomenon provides us with a simple way to electrically infer temperature: simply measure the voltage produced by the junction, and you can tell the temperature of that junction. And it would be that simple, if it were not for an unavoidable consequence of electric circuits: when we connect any kind of electrical instrument to the thermocouple wires, we inevitably produce another junction of dissimilar metals. The following schematic shows this fact, where the iron-copper junction J1 is necessarily complemented by a second iron-copper junction J2 of opposing polarity:

Junction J1 is a junction of iron and copper – two dissimilar metals – which will generate a voltage related to temperature. Note that junction J2, which is necessary for the simple fact that we must somehow connect our copper-wired voltmeter to the iron wire, is also a dissimilar-metal junction which will also generate a voltage related to temperature. Further note how the polarity of junction J2 stands opposed to the polarity of junction J1 (iron = positive ; copper = negative). A third junction (J3) also exists between wires, but it is of no consequence because it is a junction of two identical metals which does not generate a temperature-dependent voltage at all.

The presence of this second voltage-generating junction (J2) helps explain why the voltmeter registers 0 volts when the entire system is at room temperature: any voltage generated by the iron-copper junctions will be equal in magnitude and opposite in polarity, resulting in a net (series-total) voltage of zero. Only when the two junctions J1 and J2 are at different temperatures will the voltmeter register any voltage at all.

For more information about thermocouples (or any temperature sensor), contact BCE. They can be reached by calling 510-274-1990 or by visiting their web site at https://bcemfg.com.

Reprinted from "Lessons In Industrial Instrumentation" by Tony R. Kuphaldt – under the terms and conditions of the Creative Commons Attribution 4.0 International Public License.

New Epoxy Compounds Give Researchers and OEM's Design Freedom in Specifying Vacuum Feedthroughs

OEMs can no get a feedthrough to fit their design criteria.

Scientists and researchers are constantly challenged to come up with better ways to read data in a vacuum environment. Traditional ceramic and glass-to-metal vacuum feedthroughs do not offer design flexibility. Unique control and data signals must pass through the wall. In addition to passing electrical power and control signals, fiber optic cables and pneumatic tubing may be included. Always changing variables, such as the number and types of connectors, unique geometries, and limited available space, make finding an off-the-shelf feedthrough difficult. This has traditionally forced designers to compromise and specify a feedthrough with some, but not all, of the desired specifications. 

Clear epoxy feedthrough with ribbon connector.

This reality has led to significant development gains in custom epoxy feedthrough. Epoxy feedthroughs overcome design constraints. New epoxy properties rivaling ceramic and glass performance have been developed. High performance, clear epoxy potting opens the door for researchers to specify the exact number and type of wires, optical fiber cables, or any other insert that they require. Epoxy feedthrough manufacturers can provide a virtually limitless variety of wires, cables, or tubes along with the added benefit of fast prototyping and small production runs — perfect for the research and manufacturing community. 

Flanged feedthrough with epoxy potted fiber optic cable.

With the development of custom epoxy feedthroughs medical device companies, analyzer manufacturers, laboratories, aerospace companies and other R&D facilities can design their equipment based on optimum size, cost and performance, and not be forced to compromise by the limitations of ceramic and glass-to-metal feedthrough. Because of the constant pressure on "better, faster, smaller" vacuum equipment researchers and OEM designers, it's clear that epoxy feedthroughs provide flexibility and options for more efficient and creative design.

For information on epoxy vacuum feedthroughs, contact: 

BCE

https://bcemfg.com

(510) 274-1990

High Temperature Vacuum Feedthroughs

Thermocouple/Feedthrough Assemblies

Thermocouple Feedthroughs are used in many vacuum applications for temperature measurement. Thermocouples create a voltage signal from inside the vacuum system to external measuring instruments. BCE offers several standard thermocouple feedthrough designs as well as custom designs to meet your exact needs.

9 Pin Vacuum Feedthroughs

Nine pin circular feedthroughs (often called instrumentation feedthroughs) are commonly used for the transmission of low power electrical signals. They are designed for applications where typical Subminiature Type-D connections will not fit, or where there is little space. The circular geometry allows the installation of this feedthrough into very small vacuum flanges. They are often used in instrumentation applications such as semiconductor processing, electron microscopy, and a variety of analyzers.

BCE designs and builds high temperature vacuum feedthroughs for OEM and R&D. Contact them by calling (510) 274-1990, or visit https://bcemfg.com/feedthroughs.

OEM Equipment Manufacturers: Look Toward the Experienced Sales Engineer for Project Success

Original Equipment Manufacturers (OEMs) who work closely with vendor sales engineers in the design of assembly components (such as electric heating elements and vacuum feedthroughs) gain a valuable competitive advantage. By understanding what these professionals have to offer, and taking advantage of their skills, OEM designers end up with better project outcomes.

Sales engineers are a readily available resource of application knowledge. Unlike information pulled from the Internet, sales engineers possess real-time product information. They are also exposed to many different product applications and are a wealth of tacit knowledge. All readily available for sharing with their customers.

OEM design engineers often find themselves sailing in uncharted waters. In the application of electric heaters or feedthroughs for instance, designers don't always have a full grasp of heater or feedthrough design constraints. When these situations occur, the heater sales person provides a real benefit in teaching and advising the designer what is possible.  Additionally, many sales engineers have access to unpublished product and application information, which can be hugely important when attempting to build a leading edge product.

Of course any solutions proposed are likely to be based upon the products sold by the representative, but the best sales people will share the virtues of their products openly and honestly. The best sales engineers will even admit when they lack the product or experience to solve the problem, but even in this situation, you can be sure their perspective will still be of value. The goal is to build a long-term, trusting relationship - one of value to both parties. Sales engineers are in the business of dealing with people and making the important connections between customers and manufacturers. They make it their business to know what’s going on with products, companies and industries.

As an engineer or purchasing professional responsible for the design and manufacture of OEM equipment, know that working closely with a vendor sales engineer will save you precious time and greatly improve the likelihood of successful project outcomes. Their success, and your success, go hand-in-hand.

Electric Heating Elements and Electrical Feedthroughs for OEM Applications

BCE offers OEM (original equipment manufacturers) custom electric heaters, feedthroughs and BCE OEM customers benefit from decades of thermal design and applications experience. With a reputation for fast prototyping, quick turnaround for pre-production runs, and an eye for cost-effective design, equipment manufacturers quickly discover that find BCE is a long-term, highly valued supplier/partner.
sensors.

OEM Equipment Markets

• Aerospace
• Semiconductor
• Analytical Instruments
• Photovoltaic
• Medical Equipment
• Plastics Processing
• Foodservice Equipment
• Packaging

OEM Electric Heaters & Feedthroughs: Price, Delivery, Performance

Experience is Key When Applying Custom Electric Heating Elements

Heater design expertise is
readily available from your
Technical Sales Rep

Designing and applying custom electric heating elements are best completed and accomplished through the proper application of the right resources. One of the most available and important sources of high level technical knowledge is a vendor's local Technical Sales Rep. Their assistance is readily available and their consultative value is very high.  Bringing in a Technical Sales Rep will have a big bearing on a successful task or project completion.

Many Technical Sales Reps are degreed engineers. If they don't have an engineering degree, you'll find they have years of empirical application knowledge from working on many, many projects. You'll also find that many have worked at manufacturer's factories and know the in's and out's of production as well as anyone.

Consider these elements the Technical Sales Rep brings to your thermal system design project:

Watt densities? Thermal profiles?
Distributed wattage?
There's a lot to know.

Product and Application Knowledge: Your Technical Sales Rep has probably seen hundreds, if not thousands, of custom heating requirements. They deliver a mental encyclopedia of product offerings, application insights, and broad spectrum of capabilities. They also have information regarding what products are in development that can give you the competitive edge. Much of this information resides in the Reps head, and is not generally accessible to the public via the Internet.

Experience: As a project engineer, the selection and incorporation of a new heater design may be all new to you. You may be treading on fresh ground with little or no experience in the nuance of electric heaters. There can be real benefit in connecting to a knowledgeable source, with years of past design and application experience, that will save you time, money, and effort.

Access: Technical Sales Reps work closely with a variety of manufacturers, and may even have in-house prototyping or manufacturing capabilities at their own companies. This gives you, the design engineer, a connection to “behind the scenes” manufacturer contacts with essential information not publicly available. The technical sales rep knows people, and makes it his/her business to know the people that can provide answers to your electric heating and custom thermal system application questions.

So, in this age of doing your own research and self-educating on the Internet, let's not forget the importance of a face-to-face visit with someone who can really help - your Technical Sales Rep. You'll be very pleased with the information they can provide to make your job easier and the quality of your product better.

Have a custom heater job? Contact BCE now!
www.belilove.com(510) 274-1990

Ceramic Thick-Film Heaters for OEM Analytical and Medical Equipment

Ceramic heating element

Manufacturers of laboratory and process analytical equipment, as well as medical equipment, are continually challenged to make products smaller and more compact. Smaller, more efficient components are always in demand. Providing heat for sample stability or a chemical reaction is a common requirement. There's an ongoing challenge to find smaller and more efficient electric heaters.

Many traditional electrical heating elements are limited in size and efficiency due to the balance required between conductor temperatures and the the heat transfer properties of the dielectric material used in their construction. Sometimes the mass required to insulate electrically is at odds with the ability to drive the heat into the part.  Metal sheathed heaters use compacted magnesium oxide, or wafers of mica for dielectric. While these provide good electrical insulation, they also inhibit thermal transfer from resistance element to the external part. Flexible heating elements use a variety of rubbers or fluoropolymer elastomers that sandwich the resistance element. While these designs are dielectrically strong, and allow for excellent heat transfer, they are limited by the maximum operating temperatures and watt densities of the elastomer.

A newer, alternative technology is “thick-film” ceramic heaters, a process of depositing a resistor “trace” of tungsten paste on top of a ceramic part in a process very similar to screen printing. The deposition process allows for close control of thickness and width of the resistor, thus accurately controlling the conductor resistance, wattage, watt density, and uniformity of the heated part.

The use of ceramics as the heater body (referred to as a heated part), has many advantages. Ceramics are chemical inert, offer excellent thermal conductivity, impervious to moisture, and are very durable. The downside to using ceramics as heaters, however, is the difficulty in machining to very tight tolerances. In recent years though, many of the ceramic machining hurdles have been overcome through advanced ceramic machining processes.

In the early years of development thick-film ceramic heaters had a few major challenges. Dealing with mis-matched expansion coefficients between the ceramic substrate and the conductor trace was considerable. Years of research now have yielded excellent data on compatible materials making this problem much less significant. Another challenge is controlling the tolerance and repeatability of the heater resistance from part-to-part. Improvements and advancement in this area are made possible with laser etching, tighter screening procedures, and advanced machining.

The use of ceramics provided many interesting possibilities in heater design, and many materials were tested and researched. The most common ceramics used for thick-film heaters today are alumina (Al2O3), silicon nitride (Si3N4), beryllium oxide (BeO), and aluminum nitride (AlN). Each material has its own unique chemical and physical properties, but all exhibit good thermal conductivity and good dielectric properties.

The combination of excellent thermal conductivity, high dielectric, high watt densities, precise thermal profiling, and custom shapes and sizes that make thick-film ceramic heaters so attractive to equipment manufacturers. Providing more heat in smaller areas is easier than with traditional heaters. Additionally, some of the ceramics used are non-contaminating and moisture-proof, making them excellent candidates for clean and ultra-clean applications.

Ceramic thick-film heaters have many advantages over metal or elastomer sheathed heaters beyond just providing a more compact component. They are very fast acting, durable, moisture proof,  and contamination proof. They can be designed and machined to virtually any size or shape, watt density, voltage, and distributed wattage profile. While the initial design and prototyping requires investment in time and money, the resulting product can be mass produced economically and with repeatable accuracy and quality.

For more information, contact:
BCE
(510) 274-1990

www.belilove.com

Attending MD&M West and the Value of Exhibitions

Visit BCE at booth 2184

This week BCE is exhibiting at MD&M West (Medical Design and Manufacturing West) in Anaheim, CA. While the title implies medical equipment design, the exhibition also includes packaging equipment and other related equipment. The show runs Feb. 9, 10 and 11.

MD&M is the world's largest medical design and manufacturing exhibition. It "offers three days of technical presentations, hands-on design workshops, demonstrations and ticks and tricks to help you stay ahead of the game in 2016."

Representatives from many well-know "Medtech" companies will attend and a full 3 days of presentations are planned. Some of the more interesting titles are "The Creative Keys: How to Turn a Thought Into a Thing with Ease and Grace", "New Product Development Technologies and NexGen Applications", and "Leading the Smart Manufacturing Revolution".

BCE's Applied Resistance Group will showcase its thermal system design capabilities, advanced ceramics machining, laser machining, and thick film circuits and heaters. BCE is quickly developing a nation-wide reputation as an excellent partner for these products.

BCE is exhibiting their
years of experience in
thermal system design,
thick film, laser machining,
and advanced ceramics.

BCE has decades of hands-on experience with thermal systems and advanced ceramics. The result is a strong expertise in analytical instrumentation, semiconductor equipment, photovoltaic devices, medical equipment, plastics processing machinery, foodservice equipment, packaging machinery, aerospace technologies, and laboratory R&D.

Exhibitions and trade shows are great places to network and build business relationships. Face-to-face contact with prospective customers and vendors provide an opportunity for strong business relationship foundations. Meeting with someone in person is far better than meeting online.

One huge benefit of attending an exhibition is the ability to meet large numbers of helpful people in one place. When attending an exhibition, it's best to plan ahead and utilize your time efficiently. Set up appointments in advance so that you don't waste time wondering. Make a list of booths and people you really want to get to know. And please, stop by the BCE booth (2184) - you'll be glad you did.

Custom Epoxy Vacuum Feed Throughs Take It All Through The Wall

Take it all through the wall!

Equipment manufacturers and scientific researchers are continually challenged with supplying power, fiber-optic, control, and monitoring cables into (and out of) sealed vacuum vessels. Whether due to space restrictions, special geometries, or number and type of conductors, standard glass-to-metal or ceramic feedthroughs never quite fit the bill. Unfortunately, because of limited options, many designers are forced to compromise and go for an off-the-shelf solution.

Epoxy to the rescue. During the past decade, new epoxy compounds have been developed that rival glass and ceramic in performance. BCE is at the forefront of this development and leverages modern epoxy's unique properties to solve your feedthrough challenges.

For more information visit www.belilove.com/feedthrough.

Thick Film Heating Elements: An Excellent Choice for Custom OEM Thermal Designs

Custom Thick Film
Heaters and Circuits

Thick film heating elements, originally designed for the automotive and military industries, are manufactured by depositing several layers of conductor, resistors and dielectric on to an insulator via a screen printing process. The dielectric is normally some type of glass or ceramic and provides electrical insulation for the screen printed heating tracks.

Thick film heating elements are almost always custom designed for OEM applications. They can be designed in all shapes and sizes, and have an ability to provide very high watt densities with excellent controllability. The largest markets for these heating elements are appliances, analytical instruments, automotive, semi-conductor, medical device, scientific and military equipment.

Because of their inherent low mass, and their ability to carry high watt densities, thick film heaters are very efficient and are an excellent choice where a rapid heat-up (response) is required.

Advantages of thick film heaters are:

• Watt-Density up to 175 watts per sq. in. 
• Operating Temperature to 500 deg C
• Low Profile
• Excellent Control
• Very uniform heat profile
• Temperature sensors can be included on the heater
• Custom heating profiles
• Very rapid heater response
• Vibration and shock resistant
• Very customizable shapes, sizes and wattages

Basics of OEM and Industrial Electric Heating Elements - Part 2

This blog entry, reproduced from an electric heating element basics white-paper from Hotwatt, a leading US manufacturer of OEM and industrial heating elements. To download the PDF version, click this link.

Basic Heat Equations

Electric Heating Elements

It would appear at first that calculating all of the heat transfers and losses in a design would be a daunting task. Fortunately a number of equations were developed that help simplify this task. First the equations were divided into three tasks: the wattage needed to heat a material to a specific temperature in a given amount of time; the wattage needed to overcome the losses at operating temperature; and a special calculation needed to reach a melting or vaporizing point.

This equation calculates the amount of wattage (W) needed to raise the temperature of a material a specific amount in °F (ΔF) in a given number of hours (T), you first need to know the mass (m) of the material being heated and its specific heat value (c):

m × c ×ΔF

W=  -------------------

3.412 × T

The mass and specific heat of some materials may be found at www.hotwatt.com/table1.htm for metallic solids, www.hotwatt.com/table2.htm for solids other than metals, and www.hotwatt.com/table3.htm for certain liquids and gases.

Basics of OEM and Industrial Electric Heating Elements - Part 1

This blog entry, reproduced from an electric heating element basics white-paper from Hotwatt, a leading US manufacturer of OEM and industrial heating elements. To download the PDF version, click this link.

Electric heating elements
for OEM and Industry
(courtesy of Hotwatt)

The simplest definition of an electric heater is any device that changes electrical energy into heat energy. But from that simple explanation, electric heaters explode into a myriad of types, sizes, applications, and designs depending upon what’s being heated, the degree of heating needed, and the method by which the heat is applied.

The measure of electrical energy is called the Joule after its discoverer, James Prescott Joule. Through numerous experiments, Joule determined that the quantity

(Q) of heat transferred from electrical energy is proportional to the square of the current (I² ) multiplied by the resistance (R) for the period of time (t) through which it passes:

Q ∝ I² × R × t

However, one seldom sees a reference to Joules used in modern electric circuits. Instead, the controlling factor becomes that of power (P):

P = I² × R

You’ll note the only difference between the formula for determining power and that of determining Joules is the time component. The time factor in heating becomes readily apparent in any device that gets hot when an electric current flows through it: its temperature rises as time passes.